Lamp base



FIG. 1 is a perspective view of the lamp base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a perspective view of a second embodiment of my new design. 

The ornamental design for a lamp base, as shown and described. 